Moving contact of electric switches



Dec.- 2', 1952 E. BESAG ET AL 2,620,416

MOVING CONTACT OF ELECTRIC SWITCHES Filed Jan. 31, 1949 In ue tor mam WWM,

Patented Dec. 2, 1 952 UNITED STATES ram oetics Birmingham, England,assignors to J. A. Crabtree & Co. Limited, Walsall, England, a Britishcompany Application January 31, 1949, Serial No. 73,833 In Great BritainApril 24, 1948 (C1. ZOO- 166.)

2 Claims.

with its fixed contacts by overcoming the rebound of the former upon themaking of the contacts. The provision of a thin contact, preferably madeof copper, results in a relatively light mass which is coductive to theavoidance of bouncing, while the strengthening formations impartadequate rigidity to enable the employment of thin metal.

The contact is made of the thinnest metal commensurate with itsconductance, that is, the contact is of an adequate cross section tocarry the requisite current, the physical strength to compensate forthis thinness being imparted by the structural modifications in the formof flanges, ribs or the like. The provisions of these formations enablesthe employment of a relatively soft metal, such as copper, whichconstitutes an efiicient conductor.

As an example, it may be noted that for the contact strip of an electricmotor starting switch adapted to carry 15 amps, the thickness of themetal thereof has hitherto been of the order of .080 and an overallwidth of .300, this width being required for accommodating the silvercontact buttons mounted on the contact strip. According to the presentinvention, the contact strip for such a switch will have a thickness ofonly about .018".

The improvements of the present invention enable the contacts to beemployed for increased current values without impairing theirefficiency. Also the life of the contacts is increased and, hence, thenecessity for their renewal and. replacement is reduced. The productionof the moving contacts from thin sheet metal with strengtheningformations thereon, also provides a large surface area in relation tomass, for the purpose of enhancing the dissipation of heat.

In order to enable the invention to be readily understood, referencewill now be made to the accompanying drawings illustrating, by way ofexample, one construction of moving contact car- 2 rier for a three polecontactor switch, in which drawings:

Figure 1 is a perspective view.

Figure 2 is a sectional perspective View with parts disassembled.

Figure3 is a sectional elevation, the chain lines indicating the fixedcontacts and associated parts.

Figure 4 is a section on the line IVIV of Figure 3.

Figure 5 is a section on the line VV of Figure 3.

Figure 6' is a perspective view of a modified construction of movingcontact.

Figures 2-6 are drawn to a larger scale than Figure l.

Referring to Figures 1 to 5, the insulating carrier a has three verticalrecesses a in each of which is mounted a moving contact b having rivetedto each end thereof a silver button 0 for engagement with a fixedcontact d. Each moving contact 12 is formed from a thin narrow strip ofmetal having its longitudinal edges bent to form flanges e which impartstiffness and strength to the strip, and which provide a contact ofchannel section. The external flat faces of these flange e aiiord smoothguiding engagement of the contact with the side walls of the chambers orrecesses a At a short distance inwards of the buttons 0, flat stems fextend freely through the contact I), and constitute mountings forhelical compression springs 9. Each stem may be in the form of a flatarrow having the spring g coiled around its reduced part. The head f ispassed through a slot 1' in the casing while said head is disposedhorizontally as shown in the upper part of Figure 2. The stem ,1 is thenturned to the vertical position shown in the lower half of Figure 2, andits head i is passed through a keyhole slot 7c in the contact, afterwhich it is turned again to the horizontal position thus securing thecontact I) resiliently to the carrier a. Each contact 12' may be formedwith a bulge or bow b in the neighbourhood of a keyhole slot is.

According to the modified construction shown in Figure 6, the contactstrip 22 is formed with downturned flanges m at its opposite ends, inaddition to the flanges e at the sides of said strip. These end flangesm may constitute abutments for leaf or blade springs received in thechannel formed by said flanges. The flanges e and m may be formed bybending the strip b or by a drawing operation.

Instead of strengthening the strip by the for mation of flanges thereon,it may be provided with a dishing extending along a central longitudinalline. Alternatively, other raised formations may be provided for thesame purpose.

We claim:

1. In an electric switch, a pair of spaced stationary contacts; aninsulating armature carrier mounted between said contacts forreciprocation into and out of contact-closing position with the top andbottom of said carrier spaced inwardly of said contacts; an elongated,light, contact strip of thin sheet metal having strengthening formationsthereon; and means for resiliently mounting said contact strip on thefront face of the armature carrier with the end portions of said contactstrip extendin above and below the front face of said carrier and inalinement with said stationary contacts, said means comprising a stemconnected to said strip and extending through the front wall of thecarrier,

and a compression spring surrounding said stem and acting between theinner end thereof and the inner surface of the front wall of saidcarrier to resiliently maintain said strip in contact with the frontface of said carrier.

2. In an electric switch, a pair of spaced stationary contacts; aninsulating armature carrier mounted between said contacts forreciprocation into and out of contaot-c1osing position with the top andbottom of said carrier spaced a inwardly of said contacts; a contactstrip; and means for resiliently mounting said contact strip on thefront face of the armature carrier with the end portions of said contactstrip extending above and below the front face of said carrier and inalinement with said stationary contacts, said means comprising a stemconnected to said strip and extending through the front wall of thecarrier, and a compression spring surrounding said stem and actingbetween the inner end thereof and the inner surf-ace of the front wallof said carrier to resiliently maintain said strip in contact with thefront face of said carrier.

ERNST BESAG.

THOS. D. G. WINTLE.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,362,379 Whittingham Dec. 14,1920 1,809,368 Winning 1 June 9, 1931 2,211,412 Filka Aug. 13, 19402,276,698 Pierce Mar. '17, 1942 2,359,605 Ballou Oct. 3, 1944

